Help! Continuously Blowing Exhaust Gaskets - 352

Over the course of the 4+ years that I have owned my '61 Sunliner, I have replaced the exhaust manifold gaskets more times than I can remember, and this is on a car that I rarely drive. I replaced one exhaust manifold that I deemed too warped to bother having machined, and I've had a valve job done, at which time the exhaust manifold side of the cylinder heads should have been checked by the machinist (I'm assuming this here... I'm going to check the flanges this weekend when I do the gaskets, again...).

Is this a common occurance on these engines? I'm somewhat tired of this incessant and persistant problem. It seems I go through exhaust manifold gaskets more frequently than oil filters!

Thoughts????

~j.